Background

Movement clumsiness has gained increasing recognition as an important condition of childhood; however, its diagnosis is uncertain. Approaches to assessment and treatment vary depending on theoretical assumptions about etiology and its developmental course.

Over the past century, many terms have been used to describe children with clumsy motor behavior. The wide variation in labeling has depended to a large extent on cultural or professional backgrounds. For example, medical professionals use medical terms (eg, clumsy child syndrome or minimal brain dysfunction), whereas educational professionals use educational terms (eg, poorly coordinated children, movement-skill problems, or physical awkwardness).

In response to the confusing and counterproductive heterogeneity of the labels, participants at an international multidisciplinary consensus meeting in 1994 agreed to use the term developmental coordination disorder (DCD), as described in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).
[1] In 2013, the diagnostic criteria were further refined with the publication of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
[2]

The currently available data are insufficient to permit clear definition of the parameters of motor coordination difficulties in children. Various grades of severity and comorbidity seem to exist. Some children have only a relatively minor form of motor dyscoordination, whereas others have associated learning disabilities, attention deficit, and other difficulties.

In 1996, Fox and Lent reported that in contrast to the common belief that children grow out of motor coordination difficulties, such difficulties in fact tend to linger if no intervention takes place.
[3] Intervention can be beneficial if initiated during the first years of life, while the brain is changing dramatically and new connections and abilities are being acquired.

Children with multiple conditions are at greatest risk for developing behavioral difficulties over time. Some evidence supports dividing DCD into subtypes on the basis of main features, such as ability to manipulate objects, speed of movement, ability to catch objects (eg, balls thrown, struck, or kicked during sports activities), or writing ability.

A discussion about including DCD, as currently defined, into the cerebral palsy category was held.
[4] This inclusion would put DCD on the low end of the continuum of neuromotor disabilities, also described as minimal cerebral palsy, and result in a 20-fold increased incidence.
[5]

Diagnostic criteria (DSM-5)

DSM-5 classifies DCD as a discrete motor disorder under the broader heading of neurodevelopmental disorders.
[2] The specific DSM-5 criteria for DCD are as follows:

Acquisition and execution of coordinated motor skills are below what would be expected at a given chronologic age and opportunity for skill learning and use; difficulties are manifested as clumsiness (eg, dropping or bumping into objects) and as slowness and inaccuracy of performance of motor skills (eg, catching an object, using scissors, handwriting, riding a bike, or participating in sports)

The motor skills deficit significantly or persistently interferes with activities of daily living appropriate to the chronologic age (eg, self-care and self-maintenance) and impacts academic/school productivity, prevocational and vocational activities, leisure, and play

The onset of symptoms is in the early developmental period

The motor skills deficits cannot be better explained by intellectual disability or visual impairment and are not attributable to a neurologic condition affecting movement (eg, cerebral palsy, muscular dystrophy, or a degenerative disorder)

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Pathophysiology

Motor coordination is the product of a complex set of cognitive and physical processes that are often taken for granted in children who are developing normally. Smooth, targeted, and accurate movements, both gross and fine, require the harmonious functioning of sensory input, central processing of this information in the brain, and coordination with the high executive cerebral functions (eg, volition, motivation, and motor planning of an activity). Also required is the performance of a certain motor pattern.

All of these elements must work in a coordinated and rapid way to enable complex movements involving different parts of the body. At present, our understanding of motor development in humans and the pathophysiology of motor clumsiness is still in its infancy. Because of the heterogeneity in the presentation and definition of DCD, finding its cause has been difficult. A variety of theoretical models explain the role of the nervous system in motor development.

In the traditional primitive reflex model (neuromaturational theory), higher centers exert increasing control over lower reflexes. In the dynamic systems model, the central nervous system (CNS) interprets sensory feedback, and the appropriate movement strategy is selected on the basis of current experience, the state of the internal and external environment, and one’s memory of similar movements.

The neuronal group–selection model combines aspects of the 2 aforementioned models. Functional groups of neurons exist on all levels of the CNS. These groups are determined by evolution, but their functional integrity depends on afferent information produced by movement and experience. In both cortical and subcortical structures, these neuronal groups serve as early repositories for motor behavior or the receipt of specific sensory information.

Motor development is described in 2 phases. The first phase of primary variability is characterized by crude and erratic motor activity that does not require sensory information for its initiation or guidance. These self-generated movements give rise to afferent (visual or kinesthetic) inputs that reinforce more specific synaptic connections in each group.

In the second phase of motor development, sensory and motor factors interact, resulting in specific and complex muscle contraction patterns that characterize coordinated, goal-directed movement. As increasing efficient movement patterns are practiced, appropriate synaptic circuits are reinforced and subsequently established.

Adequate realization of a motion or sequence of movements requires the convergence of numerous pathways, as well as a central system in charge of integrating the information. The motor cortex, the cerebellum, and the vestibular system (which provides input about directionality, gravity, and motion) are all part of this central mechanism.

Proprioceptive information (ie, where the body is in space and how the limbs and body parts are positioned), visual input (ie, where the body is in space and where it should go), and an adequate degree of alertness (ie, activation of the reticular formation to an optimal degree) all provide information to the CNS. If one of these systems is not functioning adequately, the resulting planned movement may not be satisfactory or smooth.

The discussion below addresses some building blocks of motor functioning that are important in understanding difficulties with motor skills, their maturation, and the evaluation of children who struggle with these challenges.

Muscular tone

Muscular tone refers to the basic and constant ongoing contraction or activity in the muscles. It can be understood as a baseline or background level. Tone may be normal, too low (hypotonia), or too high (hypertonia). For example, hypotonic babies lie in a frog-leg position and appear floppy. Hypotonic infants or young children have difficulty maintaining posture against gravity and prefer to sit, leaning against something, or they may prefer to lie on the floor.

Hypotonic preschool-aged children may sit in a fashion that appears lazy; rather than sitting upright, they mostly sit in a slouching manner, leaning on the chair or a table with their head over the top of the table, or they may lie down during activities as much as possible. Of course, this positioning can also be observed in older children and is often erroneously interpreted as a sign of lack of interest or even disrespect.

By contrast, hypertonic children appear somewhat stiff and do not move in a smooth and natural way. Their movements may resemble those of a puppet or robot, and they lack the ordinarily smooth nature of movement in small motor acts. Infants may prefer to stand rather than sit and may appear to have “advanced” motor skills for their age.

Basic muscle tone that is too low or too high is one of the components of impaired motor skills. Children must fight low muscular tone to carry out movements, expending energy to maintain postures and activities. Hypertonic children may make many mistakes because of the over-activation of the muscular units.

Many children with baseline high or low tone are ultimately diagnosed with cerebral palsy, a collective term for a group of disorders affecting motor tone, movement, and posture that cause activity limitations and are due to nonprogressive disturbances that occurred in the developing fetal or infant brain.
[5]

Gross motor skills

The term “gross motor skills” refer to the ability of children to carry out activities that require large muscles or groups of muscles. Muscles or groups of muscles should act in a coordinated fashion to accomplish a movement or a series of movements. Examples of gross motor tasks are walking, running, throwing, jumping, standing on one leg, hopping, skipping, and swimming.

Posture is an important element to consider in the assessment of gross motor skills. Adequate posture may make all the difference in a child’s ability to execute a movement. This is particularly true for infants and young children. A 6-month-old infant may be able to reach for a toy if sitting but may be unable to organize this movement if the trunk is tilted in such a way that he or she must strain to maintain a vertical position.

Fine motor skills

Fine motor skills consist of movements of small muscles (eg, those of the hands, feet, tongue, lips, and face) that act in an organized and subtle fashion to accomplish more difficult and delicate tasks. Fine motor skills are the basis of coordination, which begins with transferring from hand to hand across the midline at about age 6 months.

Examples of fine motor activities are writing, sewing, drawing, putting a puzzle together, imitating subtle facial gestures, pronouncing words (which involves coordination of the soft palate, tongue, and lips), blowing bubbles, and whistling. Many children who have difficulties with their fine motor skills also find it difficult to articulate sounds or words.

Muscular strength

Muscular strength refers to the intensity of the voluntarily exerted muscle contraction that may be required to carry out an activity. Some children who struggle with motor clumsiness appear weak and slender and may have inadequate strength in their movements. Other children, on the other end of the continuum, may appear strong and muscular. Muscle strength is related to underlying tone (eg, low-tone muscles are usually weak, and weak muscles usually demonstrate low tone).

Children with hypertonicity in the leg muscles, who tend to toe-walk, may develop a higher muscular mass in the leg muscles to maintain the tiptoe position. Children who are too strong often appear brusque in their movements. Instead of softly caressing someone on the face, they may involuntarily slap the person when they are attempting to show affection. Something similar may happen when hypertonic children try to give a hug: the recipients may feel as if they are being physically crushed rather than embraced.

In contrast, a youngster with diminished muscular strength appears floppy or scrawny with thin arms, forearms, and legs. These children may execute movements that other children take for granted only at great cost. Hypotonic children cannot apply much pressure in a handshake or much force when pushing against resistance and therefore feel weak. They also fatigue easily and are unable to carry out simple tasks. For example, they may write with only thin lines and barely visible traces, and the pencil may slip out of their hand too easily.

In some cases, however, hypotonicity can be associated with normal strength (as, for example, in children with benign hypotonia or normal variations of tone). Ataxic (clumsy or poorly coordinated) children can also appear weak because truncal control affects posture, whereas poor coordination in the limbs impairs fine and gross motor tasks.

Motor planning

Motor planning involves the ability to imagine a mental strategy for carrying out a movement or an action—for instance, how to get on top of a table, how to move from point A to point B and overcome some obstacle, how to execute a dance step, or how to learn to ride a bicycle. Performing these tasks requires some planning in the sequencing of movements, including how the body and limbs will coordinate, the amount of strength that will be required, and the necessary steps that will be needed to achieve a specific goal.

Most of the time, in unaffected children, this function is achieved intuitively and without conscious effort. When children have difficulties in motor planning, however, they must carry out more conscious processing in order to complete the task.

When motor planning is impaired, parents notice that the child may frequently fall from a chair or stool, or even from a standing position, fall because anything that distracts the child’s attention can result in poor motor execution. The child seemingly lacks the intuitive ability to execute a complex movement. His or her movements may appear slow or poorly coordinated, or they may involve the use of odd strategies (eg, reaching for something that is out of reach without changing posture).

Motor planning involves a number of abilities, including the visual detection of motion and errors in movement, selection of responses, and self-corrective motions. Movements must be timed adequately, and attention and concentration are also necessary.

Sequencing and speed of movements

Sequencing and speed of movements involves the order in which movements should proceed to accomplish a desired goal. This order is mostly unconscious or intuitive. When children with DCD try to manage a complex motor act or imitate something that has been modeled, their ability to do a series of movements may be compromised.

These children often have problems with other activities that might require sequencing (eg, reading, writing their ideas, or even continuous speech). Multiple neuroanatomic structures are important for generating and then sustaining complex movements, including the motor cortices (primary, supplementary, and premotor), thalami, basal ganglia, cerebellum, sensory systems (visual, vestibular, and proprioceptive), and multiple others; defects in any of these systems can manifest as abnormal motor skills.

Children with difficulties in motor skills often perform movements slowly as a result of their difficulty in organizing and coordinating motion. They may rely on visual cues to perform the movement (eg, in handwriting) more than other children do. Their need to view the movement slows their performance.

Sensory integration

Sensory integration refers to the functioning of the brain (ie, how it manages input and produces output, including motor responses). In 1979, Jean Ayres proposed this theory that motor difficulties in children might be related to disordered sensory integration; since then, many authors, mostly in the field of occupational therapy but also in mental health, have developed this theory further.
[6]

The central concept is that children may struggle to integrate sensory input (eg, visual, auditory, tactile, and proprioceptive cues) and develop aversions (eg, to being touched or to being exposed to new sounds). Also, children may become overstimulated in any of these sensory channels, and their behavior and motor performance deteriorate in circumstances of overstimulation.

Each child has a unique profile of responses to sensory stimuli. Children with motor difficulties often have problems in the integration of sensory input, which make them vulnerable to problems resulting from sensory stimulation. These children are often referred to as having “sensory integration disorder” or “sensory processing disorder.” Sensory integration problems are associated with DCD, however, and thus these may represent variations of the same disorder.
[7]

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Etiology

Environmental, intrauterine, and genetic factors may all contribute to poor abilities in motor functioning. Comorbid conditions (eg, high levels of lead, anemia, and iron deficiency) should be ruled out.

Exposure to alcohol and drugs (eg, cocaine or methamphetamine) in utero increases the risk for motor coordination problems in the fetus. Alcohol has direct effects on the neurons of the embryo or fetus, and it has been suggested that cocaine and other stimulants may affect the contraction of arterial vessels in various areas, leading to microinfarctions (eg, in the brain of the fetus).

Another major risk factor is prematurity. The more premature the baby, the greater the potential disturbance of neuronal migration and connections, which can lead to difficulties with attention span, self-control, and self-inhibition, as well as motor coordination problems. Database reviews indicate that extremely premature infants are at significantly increased risk for developing DCD in comparison with term infants.
[8, 9] Evidence also suggests that prematurity (birth at < 37 weeks’ gestation) may be a predisposing factor.
[10]

Genetic influences may also contribute to motor coordination difficulties. For instance, 2 studies examining the heritability of DCD determined it to be 0.47-0.69 with both polygenetic and environmental factors contributing.
[11, 12] Genome-wide analysis of children with DCD suggested several genes that might contribute to the condition, but for none of these was the contributory relationship statistical significant.
[13]

In many instances, the factors mentioned above are absent; however, the child is nonetheless challenged in movements and needs special assistance to carry out everyday activities.

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Epidemiology

United States and international statistics

According to studies in different countries, the prevalence of motor coordination disorders widely varies. In some studies, rates are higher than that seen in the United States. For instance, in the United Kingdom, as many as 10% of all children reportedly have motor coordination difficulties. A conservative estimate suggests that fewer than 5% of children have the disorder worldwide; an additional 10% of children may have a minor form of the problem.

In 1998, Kadesjo and Gillberg found that motor coordination disorder frequently coexisted with poor attention span and concentration and that it was comorbid in about 6.1% of children in a sample of 409 nonreferred children in Sweden. Both disorders tended to remain stable, persisting on follow-up 8 months later. Boys were affected more frequently than girls.
[14]

In a 1996 study in Singapore by Wright and Sugden, 1.4-4% of children aged 6-9 years who were randomly sampled had difficulties in motor coordination. This study included only children with impairment in motor skills that notably interfered in their functioning in everyday life.
[15]

Age-, sex-, and race-related demographics

Disturbances in motor abilities are most evident during the school years, as children face challenges such as physical education, sports, and writing. In many cases, children with motor coordination disturbances present at an early age, and motor coordination disturbances may be detected in children younger than school age.

Boys are thought to be affected more frequently than girls, though this possibility has not been systematically studied in the United States. A population-based study from the United Kingdom looked at more than 7000 children aged 7-8 years, using more strict inclusion criteria, and reported a prevalence of 1.8% and a male-to-female ratio of 1.7:1.
[10] No evidence indicates an increased or decreased frequency of the condition according to racial groups.

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Prognosis

In the absence of intervention, children with motor coordination disorder tend to have symptoms that persist through adolescence into adulthood. Multiple follow-up studies of children with a diagnosis of motor coordination disorder have demonstrated that children do not outgrow their motor difficulties.
[16, 17, 18]

DCD does not directly lead to mortality. Children who have motor challenges may be more likely to be involved in accidents, because of the associated clumsiness; however, this clumsiness has not been shown to increase mortality.

DSM-5 cites the following conditions as commonly occurring in conjunction with DCD
[2] :

Some children with DCD become demoralized, develop poor self-esteem, and withdraw from daily activities, including those involving motor tasks (eg, drawing or writing). They may develop a feeling of being different. In some cases, children who show withdrawal behaviors are mistakenly believed to be poorly motivated, lazy, or not willing to make the effort to do a good job. Pediatricians and other health professionals must be sensitive to the signs and symptoms of emotional withdrawal arising from a child’s fear of failure and sense of hopelessness.

Children who have poor self-esteem and who accept the premise that they are lazy, incapable, or stupid require intervention from a mental health professional. Children who continue to have these feelings and do not receive help often show poor social functioning and compromised emotional development. One study specifically found that children with DCD have increased rates of learning disability in attention, social skills, reading, and spelling. Depending on their severity, these comorbidities may affect treatment options.
[19]

Intelligence quotient (IQ) may also be affected. A German study reports that the general IQ score of children with DCD was 1 standard deviation below that of children in the comparison group.
[20]

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Patient Education

Children aged 6-7 years can be positively counseled to make modifications in school and in social situations to make the best of their limitations in motor tasks. Acknowledging these limitations and helping the children understand that this problem is not voluntary on their part and not due to lack of effort or intellectual skill is important. As with other chronic medical conditions, the patient can be helped to understand the nature of the condition, to live with it, and to participate in its treatment.

Legal issues

Because definitions of conditions such as DCD are evolving, and data supporting treatment practices are lacking, legal battles may arise, particularly in the authorization, or payment for, treatment services. Having an Individualized Educational Plan (IEP) for children with DCD is important because this qualifies the child for services through the school district.

Controversy exists regarding how much accommodation should be implemented in school for a child with a motor coordination difficulty.

In a child who has severe problems writing, opinions regarding how school personnel should attempt to help differ. Some think that the child should be expected to practice extensively with the expectation that the handwriting will improve; others believe that the child should be allowed to use a word-processing keyboard exclusively. In some cases, a child with a writing problem dictates his or her thoughts to others and does not attempt to write.

These complicated decisions regarding the creation of the most responsible and effective school intervention for a given child can be decided only on a case-by-case basis after experienced professionals have performed individualized evaluations.

A controversial issue is whether adolescents with DCD should be able to obtain a license to drive a car. Adolescents are typically eager to learn to drive so that they can increase their mobility and expand their peer relationships. However, adolescents with DCD may have difficulties with right-left coordination, crossing the body midline, depth perception, or other abilities that compromise optimal driving ability.

No generalizations can be applied to this situation. A rational and responsible decision depends on an individual evaluation of the given adolescent’s abilities or difficulties and on the degree of danger of the activity.

Learning disabilities, dyslexia, and vision: a subject review. Committee on Children with Disabilities, American Academy of Pediatrics (AAP) and American Academy of Ophthalmology (AAO), American Association for Pediatric Ophthalmology and Strabismus (AAPOS). Pediatrics. 1998 Nov. 102(5):1217-9. [Medline].

Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Biomarin; Supernus<br/>Received income in an amount equal to or greater than $250 from: Biomarin; Supernus; American Board of Pediatrics.

Coauthor(s)

Aaron C Dobie, MD Resident Physician, Departments of Medicine and Pediatrics, Tulane University School of Medicine

Disclosure: Nothing to disclose.

Chief Editor

Caroly Pataki, MD Health Sciences Clinical Professor of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, David Geffen School of Medicine

Chet Johnson, MD Professor and Chair of Pediatrics, Associate Director, Developmental Pediatrician, Center for Child Health and Development, Shiefelbusch Institute for Life Span Studies, University of Kansas School of Medicine; LEND Director, University of Kansas Medical Center